Cat Design - Cold moulded Wood

[cat man do]

Originally Posted by Steven Prince

For this reason I am thinking about drawing up the basic design myself and then have someone look over them and ensure they meet the necessary regulations.

Unless you really know what you are doing i'd advise to maybe have an existing design [stock plan] re-jigged by the designer.

Someone like Bob Oram would be OK with this I would have thought.

In some instances no name boat's don't and won't hold a good resale.

Just a thought from Dave , the builder of a no name catamaran.

Dave

[Steven Prince]

44 cruising cat.

thanks very much for your input. The 60 C is a very nice boat but it has certain features i'm not keen on.

I am finding it very hard to find a boat that incorporates everything I want. The Superior 54 by Chris White and the DH550 are my current favourites, but these both have features I'm not keen on.


Dave

As the builder of a no name boat, would you, upon reflection go with a known designer for your next boat.

I expect your reason for going with a no name boat is because you couldn't find a design you liked.

Also, although I would like to have a good resale value, it is not the most important thing as I hope to have the boat for the forseable future. This is one of the many reasons why I want the design to be perfect rather than settiling for a design. Why plough all that time and effort into something you are not completly happy with.

Regards
Steven

[fhrussell]

Steven,
Don't take the designs as concrete. I'm sure the designers would be willing to work with you, designing the features you wish to see in your boat. Give them a call or email and ask if they would be open (and at what cost) to design modifications.... I'm sure they are familiar with the request.

[cat man do]

Originally Posted by Steven Prince

Dave

As the builder of a no name boat, would you, upon reflection go with a known designer for your next boat.

I expect your reason for going with a no name boat is because you couldn't find a design you liked.

n

Upon reflection, no. In This instance I had no real option, we only had $120k to throw at the project and the drawing's that I wanted would have cost the best part of $15k, and she would have been designed around more expensive Duflex and Featherlight products, so would have cost about $180k to build if I was lucky.

Having a bit of experience and spending a long time actually out there seeing what is required I felt that I knew what I wanted.

If money wasn't an issue I would have had existing Drawing's modified to suit, or indeed have had a custom design done, and have had a kit made as well, so $$$ dictated my choice.

Next time being more cashed up, this is the way I will go.


I expect I won't get as much money on sale as I would have if I built say a 50 foot Schinnong powercat, but I reckon the difference will be less than the extra it would have cost to buy said design/material's package.

For someone like youself who admit's to limited experience, I would look for a modified design to suit your need's as a first project.


Dave

[Boracay]

Now why would you want to build a catamaran, with two long narrow hulls, out of cold moulded wood?
It would seem to me that one could be built most quickly from multi chine plywood with no visible difference.

[cat man do]

Originally Posted by Chris31415

Now why would you want to build a catamaran, with two long narrow hulls, out of cold moulded wood?
It would seem to me that one could be built most quickly from multi chine plywood with no visible difference.

Plywood would usually have more stringers and frames to support the panel, where as cold moulded will be quite stiff on it's own.

In my opinion, strip plank, foam or duflex would arguably be a wiser choice on a vessel of that size for resale and for fatigue/rot resistence and weight considerations.

There would arguably be cost savings using plywood on a vessel of this size.

I believe that cold moulded could be more labour intensive, hence more expensive than most of the other option's

Northerncat [Sean], will step in shortly and smite me down for my comment's on ply

Dave

[northerncat]

i would arguably say savings on time and money when you work with ply, not to mention the thing of beauty you can construct, also dont forget that ply is its own sadnwich construction and the need for heavy if any glass is somewhat lessened
sean

[northerncat]

also extra

[northerncat]

also i think cold molding would take a bit more time than chine with stringers and frames
sean

[cat man do]

Originally Posted by northerncat

i would arguably say savings on time and money when you work with ply, not to mention the thing of beauty you can construct, also dont forget that ply is its own sadnwich construction and the need for heavy if any glass is somewhat lessened
sean

Sort of,
I think you may find that 9mm ply would not be as stiff as say 8 mm strip plank cedar, with a 440 double bias.

The ply would need additional framing compared to the cedar as well.

But I am getting picky, I certainly take your point

Dave

[Boracay]

A quick search suggests that the modulus of rupture of Western Red Cedar is 54Mpa while that of Pine is 90MPa. I would expect the surface plies of marine plywood to be superior to that of pine.
There are more interesting figures here.
An interior framework would be necessary to transfer the load from hull to crossbeam.

[Steven Prince]

I will be contacting a few designers to see about alterations shortly and will then weigh up the price against doing a design and having it proven by an engineer/ designer.

I'm open to any construction material, if the design is right.

[cat man do]

Originally Posted by Chris31415

A quick search suggests that the modulus of rupture of Western Red Cedar is 54Mpa while that of Pine is 90MPa. I would expect the surface plies of marine plywood to be superior to that of pine.
There are more interesting figures here.
An interior framework would be necessary to transfer the load from hull to crossbeam.

Missed this one and, you are right,

Ply does have a higher modulus of rupture than cedar,

Until the cedar is glassed that is.

Dave

[fhrussell]

Western Red Cedar should be thought of as a core, like foam. On its own, its light, soft and easily shaped....its point loading strength in a hull is determined by the amount of glass that covers it.
Steve, you should consider this option... strip built is quick and relatively easy. ...And will likely have a higher resale value. If resale is a main issue, foam composite will be best.
Have you considered using ply in the large flat areas of the hull and then do strip built below the waterline? Any designers out there doing this?

[cat man do]

I'm using KIRI purchased through these guy's Highpoint Timbers Homepage V2

I did some test's, drop and deflection, not overly scientific, comparing it with WRC, and end grain balsa test pieces with the same laminates as I'm using on my cat.

The KIRI came out in front on all test's.

It can be supplied in strip form and in 8 x 4 sheet's so one can glass both sides like a poor man's DUFLEX, but by using the timbers grain, you can achieve a stronger panel in one direction.

The weight was almost the same as a duflex panel, as it drink's less resin than end grain balsa, and definetly lighter than WRC.

It has a high rot resistance like WRC.

Dave